Isothermal shipping container



Feb. 22, 1955 a, E. DEI. MAR

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hlfrldfrlarl 2,702,458 Patented Feb. 22, 1955 ISOTHERMAL SHIPPING CONTAINER Bruce E. Del Mar, Los Angeles, Calif., assigner to Douglas Aircraft Company, Inc., Santa Monica, Calif.

Application August 11, 1951, Serial No. 241,474

16 Claims. (Cl. 62-101) This invention relates toshipping containers for the transportation of perishables, such as foodstuffs. It is and, to prevent conduction and convection transfer of heat to the inner box, preferably consists of hermetically Y sealed space evacuated at least to about 29.9" of mercury. For insulating the inner box from heat transfer thereinto by radiant heat energy, heat rellecting surfaces are disposed in parallelism with the faces of the boxes between the outer face of the inner box and the inner face of the outer box. Any energy passing conductively through the rst few reflecting surfaces will be reflected outwardly before it reaches the innermost one of the reflecting surfaces.

By virtue of this construction, rapid attainment of the optimum low temperature in the inner shell is assured,

especially when the inner box and the coolant vchannels are composed of a metal, such as stainless steel, since the metal-to-metal contact facilitates heat transfer and particularly concerned with the lift van," truck-size box v type of shipping container.

Such containers are usually trucked from and. to cold storage, to and from railroad flat cars onto which they are usually lifted by a crane and slings, the conventional container of this type being too heavy for shifting by hand. The cooling and insulating construction of the conventional such container makes it necessary to employ ice in bulk in order to precool the container before the perishables are placed therein, to meet'the heat evaporation into the container from the relatively warm perish ables before their journey. To preserve the perishables during their journey, numerous such reicmgs are necessary. Among the consequences is the fact that the walls of the container, in order to receive the necessarily large bulk of ice, have to be so thick that not only is the container, even when empty, usually too bulky for eiiiciei'it manhandling, but, because of these thick walls, the ratio of the usable interior volume of the container to its exterior volume is seriously reduced.

Since it requires an expensive amount of time and labor to ice up such containers, the customary practice is to initially so excessively ice it that its temperature is Y lowered to a degree far below the optimum for perishables. This excessively low temperature either freezes the perishables or causes dehydration thereof by contact therewith of the excessively cold air circulating in the container around the perishables. In either case, the salability of the goods is impaired.

The employment of conventional insulating means, such as cork or Fiberglas layers between the walls of the concentric boxes constituting the container, results in such an increase in the thickness of the container walls and in the weight of the container as to be impracticable for portable containers.

The article of the present invention is a simple but light, rugged and durable lift-van type of shipping container having a novel precooling and insulating system enabling wall spaces to be employed which are much thinner than those of a conventional container of the same exterior volume. Obviating the use of bulk ice and of conventional insulating materials, the total weight is considerably less than that of a conventional container of the same size. Among other things, the minimum effort and time required in handling the container are thereby reduced.

The improved precooling and insulating systems function in combination to entirely eliminate icing and reicing or continuous mechanical refrigeration and yet maintain the interior temperature of the container and that of the perishables very closely t o a predetermined optimum value for a relatively long time, even with the container exposed to direct heat rays.

Essentially, to achieve these and other ends, the container comprises two concentric, rigid b oxes with an improved pre-cooling system interposed inthe peripheral space between the outer wall of the interior box and the inner wallv of the outer box and comprising relatively broad and flat coolant-circulating channels disposed in direct, close contact with the entire outer surface of cach of the faces of the inner box or shell. The lateral space in the direction extending transversely to the adjacent faces of the inner and outer boxes, and lying between these coolant channels and the outer wall of the container, constitutes the insulating means for the inner box the low boundary tiln'i resistance of the coolant against the metallic walls expedites cooling considerably. The combination of the evacuated space and the reflecting surfaces assures that the established temperature will be maintained very closely within predetermined limits, since these novel insulating means assure that very little heat energy will reach the inner box.

ln order to enable loading the inner container with large, man-carried articles, such as sides of beef, and to permit these articles to be stored therein in a predeten mined attitude, a man-sized door is provided in one of the sides of the container opening into the inner container and thermal loss is minimized by constructing the door substantially as described hereinabove with referenceto the insulating means, but minus the precooling brine channels. Thermal loss around the door frame is minimized by employing plastic parts therefor and arranging thern in a novel manner.

By way of further clarification and exempliiicationv only, one of the now preferred embodiments of these and other concepts of the invention is described hereinafter in conjunction with the accompanying drawings, in which Figure l is a vertical longitudinal section of the shipping container; I

bigure 2 is a phantom perspective 'ew thereof, partly broken away, vand illustrating the disposition and construction of the pre-cooling system;

Figure 3 is a horizontal sectional view taken at one corner of the container to show the door and door-jamb construction, and

Figure 4 is a perspective view showing two of the containers mounted on a platform which may be that of a fiat-car or of an icing dock or loading platform.

The article illustrated essentially comprises two rigid,

nested shells or boxes l0 and 1l arranged preferably concentrically. Thus, the respective adjacent sides of the b oxes are spaced apart in the direction that extends at right angles to these sides leaving a peripheral space employed for novel purposes hereinafter particularized. The outer box 11 is, in this design, made up of six metallic plates 12 arranged mutually rectangularly with respect to each other to define a six sided parallelepiped. 'lhe plates thus arranged are united at their adjacent, abutting edges by clamps 13 and 14 both of which clamps may be constituted by extrusions. The clamps 13 extend the full length of the jointure and have rectangularly concave inner surfaces 13A adapted to mate the abutting plates 12 and outer ridges 13B shaped for engagement by hooks or slings for lifting and/or shifting the container. The extruded clam s 14 also extend the full length of the jointures at e lower side of the container and include ears 15 defining a guideway 16 for a wheel or similar means (not shown) by means of which to facilitate shifting the container. These clamps also include an ear 17 for engagement by slings or hooks in lifting or shifting the container. Each of the plates 12 is reinforced and rigidified against thrust loads and compression loads coming thereonto by means of a doubled sheet 18, the outer ply of which transversely corrugated, the sheets being attached at their outer edges to the adjacent edges of the sheets 12 by means of the same spacer and bolt fittings 18A that unite the clamps 13 and 14 to the outer box.

The inner container is made up of six plates 19 rectangularly arranged to dene a parallelepiped and united 19.` These means essentially include, interposed between each sheet 19 and the corresponding outer member, a dual purpose channeled, structural unit or grid 23, serving both as a refrigerant-distributing, heat exchanger unit and a reinforcing unit for the inner box thermal insulating sheets 24; transversely pillowed metallic stresstaking sheets 25; struts 26 which space sheets 25 transversely apart, and outer thermal insulating sheets 27. Each of these elements is more fully described hereinafter.

As shown in Figure 2, the stainless steel tubular frame- Works 23 not only reinforce the inner box 11 against stresses originating in the interior and exterior of the box but serve as flow-paths for the circulation of a liquid refrigerant against the outer faces of the metallic box 10'. The refrigerant is preferably a low-temperature brine and it is circulated in such'quantity for such a length of time as ,to cool the interior of box 10 to a predetermined temperature. This cooling process can occur either before the container starts on its journey or at way stations en route.; The lower ends of the channels 23 are, on each face, transversely connected by a manifold 28, here shown as a hollow triangular metallic prism. The opposite ends of the channels 23 are connected transversely by similar hollow metallic prisms 29 serving as headers. An inlet pipe 3l leads from a brine pump 32 into the peripheral space at the one corner of the shipping container,.and from this inlet, branches 33 feed the manifolds 28 of the various units 23, the branches 33 being connected at their inner ends to the one end of each of those particular three manifolds 28 the ends of which come into adjacency at this corner. An outlet header pipe 34 and outlet branches 34A are provided at the diagonally opposite upper corner of the container and are alternatively connected, by means of a conduit 35, either to a tank 36 containing pure water and chipped ice or to a brine tank 36A, as, and for purposes, later described.

The header 29 on each face of the inner box 10, except the three faces constituted by the left-end face, top face and rear face, is. as shown in Figure 2, connected to the manifold 28 of the peripherally adiacent face by connector-conduits 37. Thus. each of the three branches 33 of the brine inlet conduit directs a brine flow to only two faces before the brine exits. The brine therefore cannot undergo much temperature rise before exiting. Its efciency as a heat absorber is hence maintained throughout its flow-path in contact with the innei" box 10. This mode of passing the brine around the box 10 from the lower portion thereof to the upper also takes advantage of the natural tendencv of the brine to rise as it becomes heated. Any excess in the power necessary to pump the brine from the lower edges of the container upwardly and around the container over that required for applying it directly to the upper edges thereof and allowing it to pass downwardly by gravity, is overcome by locating the brine tank far above the pump. thus giving the pump inlet a pressure head consequent upon the gravity fall thereto from the brine tank.

Because of the direct contact of the brine in the openface metallic brine channels with the metallic sheets constituting the inner container. as well as because of the direct contact of the sheets 23 with the walls 19 and by virtue of the low skin friction of the brine against the smooth metallic surfaces of the channels and the sheets 19. rapid heat transfer is effected from the container interior to the brine and to elements 23. so that the precooling and re-cooling operations consume a relatively short time, yet are effectively accomplished.

The thermal insulating and stress transmitting sheets 24 preferablv are composed of a foam rubber and are disposed directly in coextensive. facewise contact with the entire outer. planar surfaces of each of the brinechanneling members 23 except those on the bottom. A corrugated sheet 39 is interposed between the insulating sheet 24 and the outer faces of the channels 23 and is suitably anchored at each of its edges to adjacent structure. not shown.

Tn order to insulate the inner box 10 from heat transfer thereto from exterior sources bv means of condju-tion and convection, a hermetically sealed chamber 41, preferably evacuated to at least 29.9 inches of mercury, is formed between the outer wall of the inner box and the inner wall of the outer box in circumscribing relationship to the inner box both in the longitudinal direction and in the transverse direction of the latter. In the present embodiment, this chamber is constructed essentially of inner and outer pillowed sheets 25 arranged in pairs, in mutually transversely spaced relationship, outwardly adjacent each face of the inner box. Each sheet 25 is disposed in coextensive facewise abutment with the adjacent face of one of the foam-rubber insulating sheets 24 and 27. The edges of the sheets 25, where they come into adjacency at the outer corners of the box 10 and at the inner corners of the box 11, are united, as by continuous welding seams 30, thus completing a unitary, airtight, substantially airless container circumscribing both the longitudinal and the transverse peripheries of the inner box 10. The compression-taking sheets 25 are maintained in their transversely spaced relationship by means of the transversely sectionalized struts 26, seated at each end in the axially adjacent depressions 42 between the pillows 43 of the pillowed sheets 25. The pillows being arranged in parallel rows (not shown) with the pillows in adjacent rows staggered laterally of thesheet, each end of each strut is therefore surrounded on each lateral side by a pillow. Hence, no other anchoring means is actually required for maintaining the struts at right angles to the sheets 25, or toenable them to take and neutralize compression loads yfrom the sheets 25.

For at least partially evacuating chamber 41, a anged pipe 44 is tted into an aperture 45 with the ange abutting the outer face of box 11 and with the pipe extending through the adjacent ones of members 12, 18, 27 and 25 and projecting into chamber 41. The outer end of pipe 44 is adapted .to be connected to a suitable vacuum pump,

not shown. lflra struts 26, as shown in broken section 1n Figure l.

y'are' constructed of a plurality of hollow plastic spools 46 coaxially mounted on a hollow plastic tube 47. Preferably, the plastic consists of a phenolic resin.. The adjacent anges 48 of the spools are axially spaced apart a small distance.

In order to prevent entry of radiant heat into the inner box 10, a plurality of transversely separated thin plates 49 of a reflecting material, such as polished aluminum sheets are employed. These plates are provided with apertures 51. arranged in rows extending transversely of the plate and separated longitudinally thereof, being disposed in transverse and longitudinal locations corresponding to the locations of the tubular members 47. The sheets 49 are mounted on the members 47 through apertures 51 after the spools have been successively threaded on the members 47 starting at the inner end of the latter.

The sheets 49 reect outwardly the radiant energy component of external heat-sources. Any heat which may have passed conductively through any of the outer sheets 49 will have its radiant energy component reected outwardly by the next inner sheet, and so on. The plastic struts 47 reduce heat-transmission by conduction therethrough to the minimum.

Accordingly, very little heat transfer to the precooled box 11 can occur. In fact, the actual heat rise occurring under average summer conditions over a period of six davs of exposure of a container eight feet x eight feet x fifteen feet in dimensions and pre-cooled to 32 F. is limited to 12 F.

The adiacent ends of the reecting .sheets 49 are braced and united by thicker metallic sheets 52 to confer greater strength thereon at the corners and edges of the container, where the greatest amount of impact forces may be expected, These sheets 52 also serve to reinforce and immobilize the corner struts of the reflecting unit. To substantially rigidly unify and reinforce the pillowed sheets 25, vertically elongate, substantially rigid upright metallic strips 53 are welded in contact with the inner faces thereof at each comer ofthe interior of the outer box and in contact with vertically extending hatsection reinforcing strips 55.

The inner compartment is adapted for entry by one man at a time carrying a sizeable load by means of a man-sized door 56 disposed in upright attitude in the one end well .of the article and hinged as at 57 along one edge thereof to the adiacent jamb 58 constituted by the verticalffedge of the corresponding wall of the container. The door hinges 'are disposed and constructed to enable the door to open outwardly. Thus, perishables may be either handtrucked or manually carried into the inner compartment A.

The internal construction of the door is substantially the same as that of the walls of the container, the chief difference lying in the omission from the door of the pre-cooling channels. The interior of the door thus includes a vacuumized, or hermetically sealed, space 65 inhibiting the conductive and convective transfer of heat to compartment 10A through the door. In this space 65 similar radiation reecting means 49 are disposed, and function, in the same manner as those previously described to inhibit the transmission of radiant heat energy through the door.

Airtight sealing of the edges of the door to the four sides of the door aperture is provided by means generally similar on all four sides to those illustrated in Figure 3 for the hinge side of the door. These means comprise elongate strips 59 which may be extrusions attached in transversely spaced relationship to the edge of the door and having longitudinally extending sockets 61 in which are fixed elongate, substantially hollow gaskets or seals 62 composed of a resilient material, such as hollow rubber tubing. Strikers 63, longitudinally coextensive with the members 59 are fixed on the adjacent wall of the container in positions enabling them to engage the seals airtightly when the door is closed. 'I'he strikers are xed in transversely spaced positions to mounting strips 64, which in turn are fixed at their outer ends to rigid portions of the container. Heat transfer through the metallic jambs, sill and lintel is inhibited while maintaining the wall ends airtight by means of member 65A of thermally nonconductive material such as a phenolic resin. Thermal expansion of this material, if any, is accommodated by recurved portions 66 thereof. A guard or keeper 67 for preventing damage to the strikers from hand trucks and other articles passing through the door is provided at each of the edges of the door aperture. In the present instance. the guard takes the form of a suitably shaped elongate metallic extrusion hinged at its outer end to the inner face of each of the sides of the door aperture. Each guard is adapted to be swung from the retracted position shown in Figure 3 to a position, not shown, in which it covers and protects the strikers. The interruptions or gaps in the structure of the combined vacuum chamber and reflector construction occasioned by the presence of the door are hermetically sealed by means of cap strips 68 abutting the ends of the chamber-defining plates and united airtightly thereto by;l means of clamp strip 71, shown not tightened. i

Instead of merely circulating brine through the brine channels at the outset of the containers journey in order to pre-cool the inner box and then depending on this brine and the vacuum insulation and heat reectors to maintain the desired precooled temperature, a mixture of chipped ice and pure water can be run into the empty brine channels, the mixture being frozen in these channels either by the sub-freezing residual temperature thereof or by external means, not shown. Thereby, any necessity for recoolng with brine during transit is completely obviated. Actually, Water can, if pure, be frozen in the brine channels immediately following their precooling use with the brine by merely running pure water into these empty channels. The channels, having been lowered to a temperature sufcient to lower the inner box to almost the freezing temperature, will be considerably below freezing and mere contact of pure water with these metallic channels is usually suicient to freeze the water.

Although the shipping container is capable of being constructed of the same size as conventional shipping containers, that is, with dimensions of the order of fifteen feet by eight feet by eight feet, the empty container is only about one third heavier than conventional containers of the same size but unprovided with cooling and insulating means.

With walls only 4 inches thick instead of the usual l2 inches or more, a container of the above dimensions weighs only 3000 pounds and maintains a 12,000 pound load of beef within a 12 F. preselected temperature range for seven days under average summer conditions.

Although certain details of the structural components of the container have been described in detail in order to enable the construction of a container fully capable of carrying out all the objects of the invention, it is to be understoodA that the invenon does not reside solely in the structural or constructional details and that it may be carried out in any structural manner lying within the scope of the subjoined claims.

I claim:

l. A shipping container, comprising: means defining an inner receptacle; means defining an outer receptacle surrounding the first receptacle; a multi-channel, parallelow heat absorbing unit arranged in facewise contact with each face of said inner receptacle, the several such units being now-connected in parallel; and thermal convection and thermal conduction inhibiting insulating means lying betweenthe inner and outer receptacles and surrounding the former receptacle and adapted to prevent transfer of heat by conduction and convection into said inner receptacle.

2. A shipping container, comprising: means defining an inner receptacle; means defining an outer receptacle surrounding the first receptacle; heat exchanging means surrounding the outer surface of the inner receptacle and adapted `to remove heat from the interior of said receptacle; a hollow-walled, evacuated and hermetically sealed, hollow center parallelopiped, with transversely spaced concentric inner and outer walls, said parallelopiped being disposed concentrically in the space between the inner and outer receptacles; and radiant heat-energy reflective means lying concentrically in said parallelopiped between the inner and outerwalls thereof; thereby to prevent transfer of heat to said inner receptacle by radiation, conduction and convection.

3. A shipping container, comprising: inner and outer nested receptacles, the walls of the inner receptacle being composed of a rigid, thermally conductive material; a pair of transversely adjacent walls of said container having cargo ingress and egress means therein; heat exchanging means disposed substantially coextensively with the outer surfaces of the walls'of said inner receptacle; said means including substantially rigid refrigerant conduits disposed substantially vertically onv the vertical outer surfaces of said inner receptacle and united to said surfaces so as to reinforce said receptacle against compression, tension and shear forces while conducting refrigerant in contact with said surfaces; means for circulating a refrigerant through said heat exchanging means to remove heat from the interior of said inner receptacle and reduce the temperature of said interior to a predetermined value; and insulating means for preventing heat transfer to said inner receptacle by thermal conduction, convection and radiation, said insulating means surrounding said inner receptacle outwardly of said heat exchanging means and inwardly of the inner surfaces of said outer receptacle.

4. A shipping container, comprising: inner and outer nested receptacles, the walls of the inner receptacle being composed of a rigid, thermally conductive material; a pair of thicknesswise adjacent walls of said receptacles having cargo ingress and egress means therein; heat exchanging means disposed substantially coextensivelywith the outer surfaces of the walls of said inner receptacle; a separate substantially evacuated container surrounding said inner receptacle outwardly of said heat exchanging means and inwardly of the inner surfaces of said outer receptacle, thereby to prevent heat transfer to said inner receptacle by conduction and convection; and radiant-energy reective means disposed in said evacuated container in an attitude such as to inhibit heat transfer to said inner receptacle by radiant heat energy.

5. A shipping container, comprising: inner and outer nested receptacles, the walls of the inner receptacle being composed of a stress-neutralizing and thermally conductive material; a pair of transversely adjacent walls of said container having carbo ingress and egress means therein; heat exchanging means disposed substantially coextensive with the outer surfaces of the walls of said inner receptacle; means for circulating a'refrigerant through said heat exchanging means to remove heat from the interior of said inner receptacle and reduce the temperature thereof to a predetermined value; abutted, space-defining surfaces disposed substantially coextensively with, and outwardly of. the outer surfaces of said heat exchanging means and inwardly of the inner surfaces of said outer receptacle and united hermetically at the abutting edges of said surfaces; other abutted, space-defining surfaces disposed substantially coextensively with the inner surfaces of the outer receptacle and united hermetically at the abutting edges of thesaid surfaces; and thermally non-conductive spacer means l extending transversely between each of the irst said surfaces and each of the second said surfaces in opposed relationship to the corresponding ones of the iirst said surfaces; said spacer means having their opposite ends socketed at the adjacent ones of said surfaces; whereby the hermetically sealed, spacer-braced space dened by said surfaces inhibits conductive and convective heat transfer from the exterior of said shipping container into said inner receptacle and reinforces said inner receptacle.

6. VA shipping container, comprising: inner and outer nested receptacles, the walls of the inner receptacle being composed of a stress-neutralizing and thermally conductive material; a pair of transversely adjacent walls of said container having cargo ingress and egress means therein; heat exchanging means disposed substantially coextensive with the outer surfaces of the walls of said inner receptacle; means for circulating a refrigerant through said heat exchanging means to remove heat from the interior of said inner receptacle and reduce the temperature thereof to a predetermined value; abutted, space-'defining surfaces disposed substantially coextensively with, and outwardly of, the outer surfaces of said heat exchanging means and inwardly of the inner surfaces of said outer receptacle and united hermetically at the abutting edges of saidl surfaces; other abutted, space-defining surfaces disposed substantially coextensively with the inner surfaces of the outer receptacle and united hermetically at the abutting edges of the said surfaces; and thermally non-conductive spacer means extending transversely between each of the first said surfaces and each of the second said surfaces in opposed relationship to the corresponding ones of the tirst said surfaces; said spacer means having their opposite ends socketed at the adjacent ones of said surfaces; said spacer means including a central, thermally non-conductive tubular member and a plurality vof thermally non-conductive spools mounted coaxially on said tubular member; and at least one sheet of material having an outward reflecting surface disposed between said tubular members and mounted around each of same and extending transversely of said tubular members between the adjacent ends of said spools: whereby the hermetically sealed, spacer-braced space defined by said surfaces inhibits entry of radiant heat energy from the exterior of said container to said inner receptacle. thereby to enable the walls of said inner and outerreceptacles to be transverselyqdisposed in transversely close relationship so as to increase the ratio of the volumeV of said inner receptacle toithe total outside volume of said container.

7. ln a shipping container of the type described and including a box-like. inner receptacle composed of a rigid. thermally conductive metal; a metallic uid-manifold extending along the lower portion of each of the faces of iaid inner receptacle. the inner face of said manifold ying open against the adiacent faceof said receptacle; a metallic duid-header extending along the upper portion )f each of the faces of said receptacle. the inner face of raid header lying open against the adjacent face of said 'eceptacleg hollow metallic members extending between gasket when the door is closed, thereby to prevent heat transfer between the exterior of said container and the inner receptacle throughv the edge construction of the door and door aperture; and a striker-cover hingedly mounted at its inner end to the inner face of the inner receptacle and adapted to be swung outwardly and over said striker when the door is opened.

9. The method of precooling to a predetermined temperature, the interior of a thermally conductive oontainer and maintaining said interior at said temperature for an extended time-period, comprising: circulating a liquid refrigerant in direct contact with each of the surfaces of said container for a sufficient length of time, and in sutiicient quantity, to reduce said interior to a predetermined temperature; withdrawing said re' frigerant from contact with said container; applying to said surfaces a quantity of water substantially at its freezing point sucient when frozen to maintain the precooled temperature of said container substantially at its initial value for a predetermined period of time; freezing vsaid water bycontact with said surfaces; and

, maintaining the resulting ice .in said position suliciently to preserve said predetermined temperature inv said interior of said container until said ice melts at the end of said extended time-period. v v

l0. The method of precooling to a predetermined temperature, the interior of a perature, for an extended time-period, comprising: withdrawing a fluid refrigerant V.from a s ource thereof; circulating said Arefrigerant over the entire outer suri face ofv said container in direct contact with said conhe adjacent headers and manifolds, the inner faceof aid refrigerant supplv means to the one end of each of v hose manifolds which corne into mutual adiacency at me of the lower corners of said receptacle; and means :onnecting said refrigerant outlet to the on'e end of each f those manifolds which come into mutual adiacency at ne of the upper corners of said receptacle: wherebv each f the inlet refrigerant branches is directed over only two aces of said inner receptacle before exiting from the ontainer. therehv to increase the heat absorbing ieffeciveness of said refrigerant while applying same to all the urfares of said inner receptacle.

8. Tn a shipping container of the type described and acluding inner and outer receptacles, a door constructainer for a sufficient length of time and in suicient quantity, to reduce said interior to said temperature and to cool said outer surface substantially to the freezing point of water; withdrawing said refrigerant from contact with said container; returning the. circulated refrigerant to said source for subsequent recirculation over said container; withdrawing from a source thereof a sufficient quantity of a .mixture of pure water and ice suicent, when the mixture is frozen, to maintain the precooled temperature of said container substantially at its initial value for a predetermined period of time; applyingsaid quantity of said mixture to said pre cooled container so as to effect freezing-of the mixture; and, `when said mixture melts, returning the melt to said source of pure water and ice. y

1l. A shipping container, comprising: an inner receptacle defining a cargo space; an outer receptacle; refrigerant circulating means disposed in heat absorbing relationship to said inner receptacle and cargo space and including fluid-paths embracing said inner receptacle, said fluid-paths being inlet-flow connected in parallel to a' source of pressurized refrigerant and being outlet-.How connected in parallel to a refrigerant reservoir; surfaces dening and hermetically enclosing a substantially; airless container concentrically disposed between said inner and outer receptacles; and radiant-energy reective means disposed in said airless container in surrounding relationship to said cargo space and arranged and adaptedto prevent entry of radiant-energy heat into said cargo space.

12. In an article of the type described and that includes an inner receptacle to be cooled and said receptacle having a plurality of outer-surface zones, the receptaclebeing composed of a thermally conductive ma-` terial: a refrigerant manifold of thermally conductive material arranged across the lower portion of each of said zones, the inner 4face of each of said manifolds being open and contacting the adjacent face of the receptacle; a refrigerant headery composed of heat conductive material arranged 4across the upper portion of each of said zones, the inner face of each of said headers being open and contacting the 'adjacent face of the receptacle; refrigerant-conducting, thermally conductive thermally susceptible l container and maintaining said interior at said temmembers connecting each manifold to each header, the inner face of each of said connecting members being open and attached facewse to the adjacent face of the receptacle; means flow-connecting the headers on at least half the total number of said zones to the manifold of the peripherally linearly-adjacent zone of the receptacle so as to define a plurality of parallel-dow refrigerant channels on the outer surface of the inner receptacle; tlow-establishing means connecting the refrigerant supply in parallel to the one end of each of those manifolds which come into mutual adjacency at a locus on the lower portion of said receptacle; and flow-establishing means connecting the refrigerant outlet to the one end of each of those headers which come into mutual adjacency at a locus on the receptacles upper portion which lies substantially opposite to the firstsaid locus whereby each of the main branches of inlet refrigerant is directed over only a substantially minimum area of the receptacles outer surface before exiting from the article thereby to increase the thermal effectiveness of a given volume of refrigerant while positively applying same to each of the zones of the receptacles surface.

13. In an article of the type described and including a pair of spaced, inner and outer receptacles: a closure construction for enabling ingress into, and egress from, the inner receptacle and comprising a pair of transversely adjacent walls of said receptacles, each wall having an aperture therethrough; a door hingedly mounted to the one edge-portion of the outer one of said apertures; a sealing member mounted on each of the edges of said door; a striker mounted on one of the corresponding edges of said outer aperture and adapted to sealingly engage said sealing members so as to prevent heat transfer to the inner receptacle through the closure construction aforesaid; and a striker guard hingedly mounted to the inner face of the inner receptacle and adapted to be disposed over said striker when the door is opened.

14. In an isothermal container: means defining an inner enclosure; a plurality of branches of open-face refrigerant conduits arranged in facewise contact with the exterior surface of said inner enclosure and disposer in separation on peripherally adjacent segments of tht exterior surface of said inner enclosure and together 'enveloping the exterior surface of said enclosure, no one of said branches extending substantially beyond one-half the periphery of said exterior surface; refrigerant inlet means connected in parallel to the one ter minal-portion of each of said branches; and i'efrigerant outlet means connected in parallel to the substantially opposite terrninal-portion of each of said branches whereby to etect substantially simultaneous delivery of the refrigerant to all portions of the exterior surface of the inner enclosure thereby to maintain the thermal efciency of said refrigerant substantially at its initial, or inlet, value and to expedite the rate of cooling of said enclosure with a given amount of refrigerant.

15. An isothermal container, comprising: Walls defining inner and outer spacedly nested receptacles encompassing a space surrounding the sides of the inner receptacle; a pair of concentric, hollow box-like members, each of said members being defined by rigidiied walls and the members being rigidly spaced apart so as to define a sealed annulus-like container circumscribing the walls of the inner receptacle, said annulus-like container hermetically enclosing a heat-insulating substantially evacuated space and discrete radiation-reilecting means so as to constitute the container the main thermal resistor of the device, the evacuated space and the'radiation-reecting means being so arranged with respect to the walls of said thermal resistor and with respect to each other as to constitute with said evacuated space, all the thermal barrier necessary to exclude substantially allheat from the walls dening said resistor, whereby to substantially prevent heat transfer to and from said inner receptacle.

16. An isothermal. container, comprising: walls defining inner and outer spacedly nested receptacles, said vreceptacles encompassing a space surrounding the inner receptacle; a closed and substantially evacuated con.. tainer disposed in said space in surrounding relationship to the walls of the inner receptacle; and a plurality of radiation-reecting surface-means in said evacuated container, said surface-means being mutually spaced apart transversely from each other and from the adjacent inner and outer walls of said receptacles so as to reflect radiant heat energy passing through the adjacent receptacle-wall and to inhibit emissivity-transfer and conductive transfer of heat absorbed by any one of said surface-means to the adjacent surface-means and to said walls of said evacuated container.

AReferences Cited in the tile of this patent UNITED STATES PATENTS 1,890,655 OLeary Dec. '13, 1932 1,976,879A Ewer Oct. 16, 1934 1,993,730 Carpenter Mar. l2, 1935 45,000 Smith June 23, 1936 2,119,438 OLeary May 31, 1938 2,184,380 Deibel Dec. 26, 1939 2,190,954 Stickel Feb. 20, 1940 2,196,373 Wallach Apr. 9, 1940 2,381,796 Williams Aug. 7, 1945 2,496,189 Williams Jan. 3l, 1950 2,507,379 Morrison May 9, 1950 

